Generally, motors for driving a tub of a drum type washing machine are outer rotor type DD (Direct Driving) motors. The washing machine with a DD motor is assembled in an orderly manner that a stator is coupled to a motor set assembly of a washer main body, and then a rotor to the exterior of the stator. FIG. 1 illustrates the assembly procedure of a conventional motor set.
Referring to FIG. 1, a motor set assembly 100 is shown in step (a). In the center of the motor set assembly 100 is formed a shaft 101 for rotating the rotor, with a plurality of stator assembly holes 105 formed around the shaft 101 for fixing a stator 110 to the motor set assembly 100. In step (b), a plurality of coupling bushings 111 are formed on the inner side of a stator 110, and each of them has a hole 112. The holes 112 are arranged in alignment with the stator assembly holes 105 of the motor set assembly 100 so that they are coupled to the stator assembly holes 105 through a plurality of rivets 115, in step (c). In this way the stator 110 is coupled to the motor set assembly 100. In step (d), a rotor 120 is applied to embrace the stator 110. In the center of the rotor 120 is formed a resin-molded shaft bushing 125, the center of which has a shaft coupling portion 121. In step (e), a rotor fixing bolt 126 is fitted in the shaft coupling portion 121 to complete the assembly of the motor set.
The assembly method of the conventional motor set involves applying the stator 110 to the motor set assembly 100 (in steps (b) and (c)) and then the rotor 120 to the motor set assembly 100 (in step (d)). This causes a strong friction between the rotor 120 and the stator 110 as the rotor 120 is applied to embrace the stator 110, because a plurality of magnets (not shown) coupled to the inner side of the rotor 120 have a strong magnetic attraction towards the outer circumference (i.e., teeth) of the stator 110. The friction leaves cracks on the magnets and ends up a need of replacing the whole rotor 120, resulting in a deterioration of productivity. Moreover, the worker who manually applies the rotor to the stator can be seriously injured with his/her hands accidently stuck between the rotor and stator.
To overcome the above-mentioned problems, the present invention proposes a novel rotor housing structure and a method for assembling a motor set, to improve the operation process.